You should be able to modify the column and change the primary score display to "Letter". You can then set what an A, B, C etc mean by editing the grading schema. We have a bit of a guide on this here: Using Grade Centre Grading Schemas

You should be able to modify the column and change the primary score display to "Letter". You can then set what an A, B, C etc mean by editing the grading schema. We have a bit of a guide on this here: Using Grade Centre Grading Schemas